642 



ABSORPTION. 



Fig. 254. 



Fig. 255. 



Diagram of a lymphatic gland, showing 

 the intra-glandular network, and the tran- 

 sition from the scale-like epithelia of the 

 extra-glandular lymphatics, to the nu- 

 cleated cells of the intra-glandular. 



Portion of the intra-glandular lymphatic, 

 showing along the lower edge the thick- 

 ness of the germinal membrane, and upon 

 it, the thick layer of glandular epithelial 

 cells. 



tlie centre of the gland, becomes gradually thinner towards the afferent 

 and efferent vessels, and passes continually into the ordinary epithe- 

 lium. 



The thoracic duct, g, Fig. 250, and 13, Fig. 253, is formed by the 

 junction of the chyliferous trunks with the lymphatic trunks from the 

 lower extremities. The receptaculum chyli, already described, forms 

 its commencement. After passing from under' the diaphragm, the duct 

 proceeds, in company with the aorta, along the right side of the spine, 

 until it reaches the fifth dorsal vertebra; where it crosses over to the 

 left side behind the oasophagus. It then ascends behind the left carotid 

 artery ; runs up to the interstice between the first and second vertebrae 

 of the chest; where, after receiving the lymphatics, which come from 

 the left arm and left side of the head and neck, it suddenly turns down- 

 wards, and terminates at the angle formed by the meeting of the sub- 

 clavian and internal jugular veins of the left side. 



To observe the chyliferous apparatus to the greatest advantage, it 

 should be examined in an individual recently executed, or killed sud- 

 denly two or three hours after having eaten ; or in an animal, destroyed 

 for the purpose of experiment, under similar circumstances. The lac- 

 teals are then' filled with chyle, and may be readily recognised, especially 

 if the thoracic duct has been previously tied. These vessels were un- 

 known to the ancients. The honour of their discovery is due to Gaspard 

 Aselli, 1 of Cremona, who, in 1622, at the solicitation of some friends, 

 undertook the dissection of a living dog, which had just eaten, in order 

 to demonstrate the recurrent nerves. On opening the abdomen, he 

 perceived a multitude of white, very delicate filaments crossing the 

 mesentery in all directions. At first, he took them to be nerves; but 

 having accidentally cut one, he saw a quantity of a white liquor exude, 

 analogous to cream. Aselli also noticed the valves, but he fell into an 

 important error regarding the destination of the lacteals ; believing them 

 to collect in the pancreas, and from thence proceed to the liver. In 

 1628, the human lacteals were discovered. Gassendi 2 had no sooner 

 heard of the discovery of Aselli, than he spoke of it to his friend 

 Nicholas-Claude-Fabrice de Peiresc, senator of Aix; who seems to have 

 been a most zealous propagator of scientific knowledge. He immedi- 



1 De Lactibus seu Lacteis Venis, &c., Mediol., 1627; also, in Collect. Oper. Spigelii, edit. 

 Van der Linden; and in Manget. Theatr. Anatom. 



2 Vita Peirescii, in Op. omnia, v. 300. 



